A generic ground milling machine, especially a cold milling machine, a stabiliser or recycler, having a cooling system is known, for example, from DE 103 47 872 C5. Such ground milling machines are frequently used in road and path construction as well as for subgrade stabilisation. Their working device is a cylindrically shaped milling drum which is equipped on its outside circumference with a plurality of milling tools. In working operation of the ground milling machine, the milling drum is made to rotate and the milling tools arranged on the milling drum are driven into the ground, for example, a road surface. The ground or asphalt layer of a road to be processed is thus broken up and crushed. The produced milling material is usually conveyed by a discharge conveyor either in or against the working direction of the ground milling machine to a transport vehicle and is removed by said vehicle.
Generic ground milling machines typically comprise an internal combustion engine as a drive unit, for example, a diesel engine, which is arranged in an engine compartment. The engine compartment designates a substantially enclosed arrangement compartment of the ground milling machine, in the interior space of which the internal combustion engine is arranged. The internal combustion engine is used on the one hand to rotate the milling drum in working operation of the ground milling machine via a milling gear which is mechanical, for example. On the other hand, the internal combustion engine provides the drive power required for travelling operation, for example, by driving a pump transfer gear, which on its part supplies a hydraulic system with at least one hydraulic pump with power. The hydraulic system drives the running gear among other things, for example, specifically the wheels or crawler tracks. The pump transfer gear thus concerns a functional unit for power splitting, via which the drive motion of the internal combustion engine, for example, of its crankshaft, can be distributed to several consumers, especially the hydraulic pumps. Such pump transfer gears frequently constitute a structural unit.
Considerable heating phenomena occur during the operation of such soil milling machines, for example, obviously, at the internal combustion engine, in the hydraulic circuit, etc. Ground milling machines therefore typically comprise a cooling system with an engine cooling device and a hydraulic fluid cooling device. The engine cooling device comprises a first fan, for example, and a cooling circuit with an engine heat exchanger. A cooling liquid is circulated in said cooling circuit, for example, via which the internal combustion engine can be cooled in operation. The heat absorbed by the cooling liquid is dissipated at the heat exchanger to the air. The hydraulic fluid cooling device is implemented in such a way that it enables a cooling of the hydraulic fluid that is heated up during operation. The hydraulic fluid cooling device is frequently arranged in such a manner that it uses cooling air of the engine cooling device for cooling purposes.
It is known for such ground milling machines that a first cooling air duct is present, which is formed in such a manner that cooling air aspirated from the outside environment by the first fan is guided to the engine heat exchanger and subsequently to a first cooling air outlet. The cooling air guided in the first cooling air duct can further be guided through a hydraulic fluid cooling device. However, this partly considerably reduces the total cooling power of the cooling system, since, in this case, only cooling air that has already been heated to some extent is available for the hydraulic fluid heat exchanger, for example. For this reason, it is known from the prior art to use considerably oversized fans in order to provide the entire required cooling air for the engine cooling device and the hydraulic fluid cooling device. This leads to a high power demand of the fan and thus especially also to a comparatively high share in the fuel consumption which is incurred for the operation of the fan alone.
A method for cooling the internal combustion engine arranged in an engine compartment and the hydraulic system of a ground milling machine comprises the intake of cooling air in a first cooling air duct by a first fan, for example. The cooling air of the first cooling air duct is conducted in the prior art through an engine cooling device with an engine heat exchanger, and, thereafter or before, through a heat exchanger of a hydraulic fluid cooling device. The cooling air is then ejected through a cooling air outlet. A fluid such as cooling water or hydraulic oil flows through the heat exchangers, which are arranged in such a way that they have the greatest possible surface over which the cooling air can be conducted in order to transfer waste heat from the fluid to the cooling air and to remove said heat. It is the object of the cooling air to convey waste heat from the ground milling machine to the ambient environment. The waste heat originates from the internal combustion engine, for example, which also frequently heats the cooling water of a cooling circuit via a heat exchanger. This basic configuration of cooling circuits, both for the internal combustion engine and also for the hydraulic system, is known from the prior art.
In the ground milling machines and methods for cooling as known from the prior art and as described above, it is disadvantageous that oversized cooling devices are regularly used in order to ensure efficient cooling both of the internal combustion engine and also the hydraulic fluid even under peak loads. Furthermore, already heated cooling air is partly used for further cooling, resulting in a higher fan power being necessary for achieving the desired cooling power.
It is the object of the present invention to solve the problems of the prior art. It is specifically the object of the present invention to provide a ground milling machine with a cooling system, such a cooling system and a method for cooling a ground milling machine which enable an especially efficient, reliable and at the same time energy-saving cooling.